Year	% (national estimate)
1960	38.2
1961	37.9
1962	38.3
1963	37.6
1964	38.2
1965	39.2
1966	41.9
1967	43
1968	43.8
1969	45.8
1970	45.7
1971	44.7
1972	46.4
1973	48.8
1974	49.6
1975	48.3
1976	49.6
1977	51.2
1978	53.8
1979	54.8
1980	53.9
1981	53.3
1982	52
1983	52.2
1984	54.4
1985	55.4
1986	56
1987	57.1
1988	57.6
1989	57.7
1990	56.1
1991	54
1992	53.7
1993	54.3
1994	55.34
1995	55.131
1996	55.263
1997	56.051
1998	57.16
1999	56.957
2000	57.379
2001	56.043
2002	54.276
2003	52.466
2004	52.225
2005	52.641
2006	52.251
2007	51.801
2008	50.18
2009	47.007
2010	45.074
2011	44.896
2012	45.401
2013	46.033
2014	47.059
2015	48.198
2016	48.763
2017	49.877
2018	50.339
2019	51.097
2020	45.317
2021	49.673
2022	50.564
2023	51.951